In the rotary kiln, which is part of a solid heat carrier process, the thermal decomposition of the organic mass of fuel takes place. In the rotary kiln, dry oil shale is mixed with the hot heat carrier and it remains in the rotary kiln for a certain period until heat exchange occurs between the oil shale and the heat carrier, resulting in the pyrolysis of oil shale. At high temperature and at over pressure pyrolysis of oil shale results in formation of gaseous and solid products, which are further processed in subsequent processing steps.
To improve the efficiency of the pyrolysis process, for better mixing of the oil shale and ash, but also to ensure the forward movement of the material from the input end to the output end of the rotary kiln, the rotary kiln is constantly rotating.
The rotary kiln is a drum with internally refractory lined parallel walls that rotates on four carrying rollers. There are openings at both ends of the rotary kiln for feeding the material to be processed (oil shale and ash) and releasing the semicoke and gaseous products.
Attaching the rotating input/output ends 17′ with fixed units or elements of adjacent units is performed with the use of special end sealing assemblies and end sealings (see FIG. 1).
The mentioned end sealings compensate for the radial movement of the ends and the longitudinal increase due to the temperature changes of the rotary reactor.
End sealings of the rotary kiln have the following purposes:                Sealing the terminal joints between the pressurized rotary kiln and fixed units while rotating and avoiding the vapour-gas mixture from leaking to the surrounding atmosphere via terminal joints which are between the rotating drum and mixing chamber and the rotating drum and separator of solid particles from vapour-gas mixture or dust chamber;        Lubricating the working surfaces of end sealings;        Cooling the construction of end sealings;        Compensating for the longitudinal expansion and radial movement due to the temperature changes of the reactor.        
The constructions of input end sealing and output end sealing of the existing rotary kiln are different with respect to the sizes of cast iron casing rings 2′ and 3′ (see FIG. 1). The cast iron casing rings used in said sealings have different diameters in the known construction. In addition, the casing rings have a different thickness and the lubricant channels have a rectangular cut in the known solution. In the technical solution in use, connecting the casing ring 1′ coaxially with cast iron casing rings forms lubricant channels 8′ and 9′ in which the lubricant is meant for lubricating the working surfaces and also cooling the construction of the pair of the working rings. FIG. 1 depicts the technical solution of the end sealings of the existing rotary kiln in which a casing ring 1′ is attached to the flange 12′, which is attached to the outside of the rotating drum 15′ of the rotary kiln, and the first casing ring 2′ is attached to the flange 10′, which is attached to the outside of the fixed input/output unit 17′, and using appropriate attachment means, the second casing ring 3′ is attached to the other side of the rotating casing ring 1′. For the sake of clarity, in the figures describing the present invention, same position numbers with an apostrophe added are used with the same construction elements.
Considering the fact that during the working process of the rotary kiln, there is over pressure in the whole rotating drum of the solid heat carrier retorting unit, thus, in terms of environmental safety, it is especially important that the joints of the rotary kiln and those of the fixed units that are connected to it ensure a sufficient thickness, so that the gases with different chemical composition produced during the retorting process would not leak into the surrounding environment.